diff --git a/doc/build.py b/doc/build.py
index 663b0fc1..cdcea691 100755
--- a/doc/build.py
+++ b/doc/build.py
@@ -97,7 +97,7 @@ def build_docs(version='dev', **kwargs):
               '-Aversion=' + version, '-Aversions=' + ','.join(main_versions),
               '-b', 'html', doc_dir, html_dir])
   try:
-    cmd = ['lessc', '--clean-css',
+    cmd = ['lessc', '--verbose', '--clean-css',
            '--include-path=' + os.path.join(doc_dir, 'bootstrap'),
            os.path.join(doc_dir, 'fmt.less'),
            os.path.join(html_dir, '_static', 'fmt.css')]